The present invention generally relates to drum compressor rotors as used in gas turbine engines, and more particularly to an improved structural reinforcement of a drum compressor rotor.
Referring to FIGS. 3 and 4 there is shown diagrams of a basic drum compression stage rotor 100 for a gas turbine engine comprising a hub 102, fan blades 104 and a shaft (not shown) generally having an interference fit with the rotor hub 100. The compressor rotor is journaled within a housing and acts in conjunction with a compressor stator to generate very high velocity output airflow from a low velocity input airflow. The high velocity output airflow is subsequently fed to a combustor stage of the turbine. The rotor is typically one-piece cast with the shaft bore, mounting surface and blade tip diameters being machined. Basic cast material conventionally consists of a metal or metal alloy such as common steel, aluminum, nickel or titanium alloys.
Turbine compressor rotors typically operate at an extremely high rpm. A problem which generally arises to affect turbine performance is the strength-to-density ratio of the metal alloy employed in the rotor hub limits the rotor's maximum operating speed. As shown in FIGS. 3 and 4, the prior art in general has structurally reinforced the hub by welding metal or metal alloy disk supports 106(a-c) inside the hub to provide increased radial hub strength. This reinforcement of the hub increases the maximum operating speed of the rotor thereby permitting improved turbine performance.
However, the use of the metal or metal alloy disk supports has a drawback of being an expensive, complicated and time-consuming procedure when making the rotor. Each disk must be precisely located and held when welding to the hub. Further, since the inner surface of the hub is cast (i.e. a rough surface), the diameter of the disk supports must be slightly smaller than the inner hub surface. The weld is then made around the outer edge of the disk as a build up or filler (shown as 108 in FIG. 4 ). Thus, the structural support is limited to the strength of the weld.
The metal support disks also suffer the drawback of making the compressor rotor heavy. This added weight reduces turbine performance by increasing the amount of time to accelerate from rest to operating speed for the compressor rotor. The added weight is also undesirable due to the increase in the overall weight of the compressor.